New synthetic and characterization strategies for polyolefins

Thesis (PhD)--University of Stellenbosch, 2006.ENGLISH ABSTRACT: Metalloxycarbene complexes [(CO)5M1=O(R)M2(Cl)L2] (M1 = Cr , W; M2 = Zr, Hf; L = Cp, Cp*) were synthesized from the reaction between anionic Fischer-type carbene complex salts [(CO)5M1=C(O)R][NEt4] and metallocene chlorides. The molecular and crystal structures of [(CO)5W=C(Me)OZr(Cp)2Cl], [(CO)5Cr=C(Me)OZr(Cp)2Cl] and [(CO)5W=C(Ph)OHf(Cl)Cp2] determined by X-ray methods, show a short Ccarbene-O and relatively long O-Zr and O-Hf separations. Metalloxycarbene complexes in the presence of MAO are active catalysts for homo- and copolymerization of -olefins and produce polymers with heterogeneous properties. 1-Pentene oligomers, homopolymers of ethylene and ethylene/1-pentene copolymers were successfully synthesized using metalloxycarbenes/MAO and the results obtained were critically compared with those synthesized with metallocene/MAO catalysts. The GC and GPC show that 1-pentene oligomers produced with both metalloxycarbenes and metallocenes catalysts range from simple dimers to more complicated high molecular weight (2 600 g/mol) products. The properties of polyethylene and ethylene/1-pentene copolymers were evaluated by, among others, GPC, SEC-FTIR, preparative molecular weight fractionation and HPer DSC. Generally the polymers obtained using metalloxycarbene/MAO catalysts have broad and bimodal molecular weight distributions. The copolymers have higher concentration of 1- pentene in the lower molecular weight fraction than those produced with metallocene/MAO as shown by SEC-FTIR. Consequently, HPer DSC shows a decrease of melting and crystallization temperature towards the low molecular weight fractions.AFRIKAANSE OPSOMMING: Metaaloksikarbeenkomplekse [(CO)5M1=C(R)OM2(Cl)L2] (M1 = Cr , W; M2 = Zr, Hf; L = Cp, Cp*] is gesintetiseer in die reaksie tussen anioniese Fischer-tipe karbeenkomplekssoute, [(CO)5M1=C(O)R][NEt4], en metalloseen dichloriedes. Die molekulêre- en kristalstrukture van [(CO)5W=C(Me)OZr(Cp)2Cl], [(CO)5Cr=C(Me)OZr(Cp)2Cl] en [(CO)5W=C(Ph)OHf(Cl)Cp2] bepaal deur X-straalkristallografiese metodes, toon die aanwesigheid van kort Ckarbeen-O- en relatief lang O-Zr- en O-Hf-bindings. Metaaloksikarbeenkomplekse, in die aanwesigheid van MAO, is aktiewe katalisatore vir die homo- en ko-polimerisering van α-olefiene en is verantwoordelik vir die vorming van polimere met heterogene eienskappe. 1-Penteen oligomere, homopolimere van etileen en etileen/1-penteen ko-polimere is suksesvol gesintetiseer met metaaloksikarbeenkomplekse/MAO en die resultate sodoende verkry, is krities vergelyk met produkte gesintetiseer vanuit metalloseen/MAO prekatalisatore. Die GC en GPC resultate toon dat die 1-penteen oligomere, geproduseer met beide metaaloksikarbeenkomplekse en metallosene, kan wissel van eenvoudige dimere tot meer komplekse, hoë molekulêre massa (2 600g/mol) produkte. Die polietileen en etileen/1- penteen ko-polimere is gekarakteriseer deur onder andere gevorderde, GPC, SEC-FTIR, preparatiewe molekulêre massa fraksionering en HPer DSC. In die algemeen het die polimere verkry met metaaloksikarbeen/MAO katalisatore, breë en bimodale molekulêre massaverspreidings. Die ko-polimere bevat hoër konsentrasies van 1-penteen in die lae molekulêre massa fraksie in vergelyking met dié gevorm vanuit metalloseen/MAO–gekataliseerde mengsels, soos aangedui deur SEC-FTIR-analise. HperDSC wys 'n verlaging in smelt- en kristallisasietemperature in die laer molekulêre massa fraksies

ARIMA forecasts of the number of beneficiaries of social security grants in South Africa

The main objective of the thesis was to investigate the feasibility of accurately and precisely fore- casting the number of both national and provincial bene ciaries of social security grants in South Africa, using simple autoregressive integrated moving average (ARIMA) models. The series of the monthly number of bene ciaries of the old age, child support, foster care and disability grants from April 2004 to March 2010 were used to achieve the objectives of the thesis. The conclusions from analysing the series were that: (1) ARIMA models for forecasting are province and grant-type spe- ci c; (2) for some grants, national forecasts obtained by aggregating provincial ARIMA forecasts are more accurate and precise than those obtained by ARIMA modelling national series; and (3) for some grants, forecasts obtained by modelling the latest half of the series were more accurate and precise than those obtained from modelling the full series.Department of StatisticsM.Sc. (Statistics

Penta­carbonyl-2κ5 C-chlorido-1κCl-bis­[1(η5)-cyclo­penta­dien­yl](μ-α-oxido­benzyl­idene-1:2κ2 O:C)titanium(IV)tungsten(0)

The title compound, [TiW(C5H5)2(C7H5O)Cl(CO)5], consists of two metal centres, with a (tungstenpenta­carbon­yl)oxy­phenyl­carbene unit coordinated by a titanocene chloride. The oxycarbene group is nearly planar, with the phenyl ring twisted by an angle of 39.1 (2)° with respect to this plane. One of the cyclo­penta­dienyl rings undergoes an offset face-to-face π–π inter­action [3.544 (6) Å] with the symmetry-related cyclo­penta­dienyl ring of a neighbouring mol­ecule

Synthesis and characterization of homo- and copolymers of a-olefins using metallocene catalysts

Thesis (MSc)--Stellenbosch University, 2002.ENGLISH ABSTRACT: This study comprises the synthesis and characterization of propene/lower a-olefin copolymers and a-olefm homopolymers using metallocene catalyst systems. Incorporation of a-olefin comonomer into the polypropene backbone led to a change in properties such as microstructure and melting and crystallization temperatures. Synthesis of propene/a-olefin (J-butene, l-pentene, l-hexene and 4-menthyl-l-pentene) copolymers was carried out using the Me2Si(2-Methylbenz[e]indenyl)2ZrChIMAO catalyst combination. Copolymers were characterized by NMR, GPC, DSC and CRYSTAF. Comonomer incorporation was generally kept below 6 % to ensure crystallizable copolymers. Comonomer content influences tacticity. It was especially pronounced for propenell-butene copolymers and attributed to the formation of clusters. Melting and crystallization temperatures, (Tm (DSC), Tc (DSC) and Tc (CRYSTAF)), of propene/lower a-olefin copolymers decreased linearly with an increase in comonomer incorporation and strongly depend on comonomer type displaying a different behaviour compared to that of propene/ higher a-olefins (l-octene, I-decene, l-tetradecene, and 1- octadecene) copolymers. The melting and crystallization temperatures of propene/4- methyl-l-pentene copolymers occur between those ofpropene/l-pentene and propenellhexene. Poly-n-olefins (l-pentene, l-hexene, l-octene and l-decene) were prepared using a series of (R-115_C9H6)2ZrChIMAO[R = benzyl, phenyl and Si(CH3)3] and Me2C(115-C5H4-115- C9H6)ZrCh/MAO catalysts under different conditions. The resulting oligomers and polymers were characterized by GPC and NMR. Better conversions were obtained using catalysts with less bulky substituents and high MAO/catalyst ratios. Products ranged from dimeric oligomers to poly-u-olefins with molar masses between ca. 300 g.mol" and 6000 g.mol". Polydispersities, MwlMn, of poly-n-olefins synthesized at room temperatures were approximately 2, however, higher polydispersities were obtained at higher temperatures. Various end groups such as vinylidene, 1,2 disubstituted and 1,1,2 trisubstituted double bonds were observed and attributed to different propagation and termination reactions. The most important vinylidene end group corresponds to a specific 1,2 monomer insertion and termination by p-elimination.AFRIKAANSE OPSOMMING: Hierdie studie behels die sintese en karakterisering van propeen/laer-a-olefien kopolimere en a-olefien homo-polimere wat berei is deur van metalloseen-katalisatore gebruik te maak. Die insluiting van 'n a-olefien ko-monomeer in die ruggraat van propileen het 'n verandering in eienskappe soos mikrostruktuur, smelting en die temperatuur van kristallisasie tot gevolg gehad. Die sintese van propeen/a-olefien (l-buteen, I-penteen, I-hekseen en 4-metiel-lpenteen) ko-polimere is uitgevoer met die katalisatorkombinasie Me2Si(2-Metielbenz[e] indeniel)2ZrClzIMAO. Daar is gepoog om die inkorporasie van die ko-monomeer tot <6% te beperk, om sodoende kristalliseerbare ko-polimere te verseker. Die komonomeerinhoud beïnvloed taktisiteit. Dit was veralopvallend in die propeen/l-buteen ko-polimere, en is toegeskryf aan die vorming van trosse (klusters) Die ko-polimere is gekarakteriseer deur van KMR, GPK, DSK en KRISTAF gebruik te maak. Die smelt-en kristallisasie-temperature (Tm (DSC), Tc (DSC) en Tc (CRYSTAF») van die propeen/Iaer-n-olefien ko-polimere het lineêr afgeneem met 'n toename in ko-monomeer inkorporasie en het sterk afgehang van van die tipe ko-monomeer. Die gedrag van laasgenoemde ko-polimere het verskil van dié van die propeenlhoër-a-olefien kopolimere (l-okteen, I-dekeen, I-tetradekeen, en l-oktadekeen). Die smelt- en kristallisasie-temperature van die propeen/4-metiel-l-penteen ko-polimere lê tussen dié van propeen/l-penteen en propeen/l-hekseen. Die poli-a-olefiene (l-penteen, I-hekseen,l-okteen en I-dekeen) is onder verskillende reaksiekondisies berei deur van die katalisatore (R-115-C9H6)zZrChIMAO [R=bensiel, feniel en Si(CH3)3] en Me2C(115-C514-115-C9H6)zrChIMAO.gebruik te maak. Die nuwe oligomere en polimere is met behulp van GPK en KMR gekarakteriseer. Katalisatore met kleiner substituente en hoër MAO/katalisator-verhoudings lewer beter omskakelings. Produkte het gevarieer vanaf dimeriese oligomere tot poli-a-olefiene met molêre massas tussen 300 en 6000 g.mol'. Die polidispersie van die poli-a-olefiene by kamertemperatuur gesintetiseer was ongeveer 2; hoër polidispersies is egter by hoër temperature verkry. Vinilideen, 1.2-disgesubstitueerde- en 1,1,2-trigesubsidueerde dubbelbindings is as eindgroepe waargeneem. Dit is toegeskryf aan verskillende voortplantings- en termineringsreaksies. Die belangrikste vinilideen-eindgroep stem ooreen met 'n spesifieke 1,2 monomeerinvoeging en terminering deur p-eliminasie

Research funding and modes of knowledge production : a comparison between NRF-funded and industry-funded researchers in South Africa

Thesis (PhD)--Stellenbosch University, 2014.ENGLISH ABSTRACT: The changing South African policy context since 1994 (new science and innovation policies), and institutional changes at the National Research Foundation (NRF) have had an effect on different funding instruments and related modes of knowledge production. In this study we compare the modes of knowledge production utilized by researchers funded by the NRF and those funded by industry. We also compare the level of scientific productivity of these groups. This study makes two major contributions: first, we provided a reconstruction of the history of research funding in South Africa from 1918 (through the Research Grant Board – RGB), to date (through the NRF established in 1999 as a result of the merger of the Foundation for Research Development (FRD) and the Centre for Science Development (CSD). The second major contribution of this study concerns the relationship between funding sources and modes of knowledge production and dissemination. We found evidence that there is an increase in third stream funding for university research in South Africa. The study shows that respondents who received funding from both the Focus Areas and THRIP, concurrently, produced more average annual research outputs than those who received funding from either the Focus Areas or THRIP only. When we compared respondents who only received the Focus Areas or THRIP grant, we found that those who received the Focus Areas grant published more outputs annually than THRIP-funded researchers, despite the fact that those who received the THRIP grant had larger grant amounts, on average, than their Focus Areas-funded counterparts. We also found that industry/THRIP funding is utilised on problem-solving type of research, i.e. applied research, while public/NRF funding is utilised on basic/fundamental/curiosity-driven research. Overall, the findings show that there is no clear cut conclusion about the influence of funding on the mode of knowledge production. We could not prove that the two factors, that is, funding and mode of knowledge production, are related in a linear fashion. This is a much more complicated situation that requires more investigation.AFRIKAANSE OPSOMMING: Die veranderende Suid-Afrikaanse beleidskonteks sedert 1994 (nuwe wetenskap- en innovasiebeleid), sowel as institusionele veranderinge aan die Nasionale Navorsingstigting (NNS), het 'n uitwerking gehad op verskillende befondsingsinstrumente en verwante vorme van kennisproduksie. In die lig hiervan vergelyk die huidige studie die vorme van kennisproduksie van navorsers wat deur die NNS befonds word met dié van navorsers wat deur die bedryf befonds word. Die twee groepe se onderskeie vlakke van wetenskaplike produktiwiteit word ook vergelyk. Die studie lewer twee belangrike bydraes. In die eerste plek bied dit 'n rekonstruksie van die geskiedenis van die finansiering van navorsing in Suid-Afrika, vanaf 1918 (deur die Navorsingstoekenningsraad), tot en met vandag (deur die NNS wat in 1999 tot stand gekom het met die samesmelting van die destydse Stigting vir Navorsingsontwikkeling – SNO – en die Sentrum vir Wetenskapsontwikkeling – SWO). Die tweede belangrike bydrae van hierdie studie is die ondersoek na die verband tussen befondsingsbronne en verskillende vorme van kennisproduksie en -disseminasie. Die resultate van die ondersoek dui op 'n toename in derdegeldstroom-befondsing wat universiteitsnavorsing in Suid-Afrika betref. Die studie toon verder dat respondente wat befondsing van beide die fokusarea- en THRIP-programme ontvang, se gemiddelde jaarlikse navorsingsuitsette beduidend hoër is as dié van respondente wat slegs binne een van die twee programme befonds word. ʼn Vergelyking van die navorsingsuitsette van respondente wat slegs fokusarea-befondsing ontvang en respondente wat slegs THRIP-befondsing ontvang, toon dat diegene met fokusarea-befondsing se jaarlikse publikasieuitsette gemiddeld hoër is, ondanks die feit dat die THRIP-toekennings groter bedrae behels. Daar is ook gevind dat befondsing deur die bedryf/THRIP gebruik word vir navorsing wat gerig is op probleemoplossing, d.w.s. toegepaste navorsing, terwyl publieke of NNS-befondsing aangewend word vir basiese/ fundamentele/nuuskierigheid-gedrewe navorsing. Die algehele beskouing is dat geen duidelike gevolgtrekking gemaak kan word met betrekking tot die invloed van befondsing op die vorme van kennisproduksie nie. Daar kan nie onomwonde gestel word dat die twee kernfaktore van ondersoek, naamlik befondsing en vorme van kennisproduksie, reglynig met mekaar verband hou nie. Die situasie is meer kompleks en vereis verdere navorsing

An improved model for provision of rural community-based health rehabilitation services in Vhembe District of Limpopo Province, South Africa

PHDRDVInstitute for Rural DevelopmentInstitute for Rural Development and Poverty Alleviatio

Distribution and impact of the Argentine ant, Linepithema humile (Mayr), in South Africa

Thesis (MScAgric)--University of Stellenbosch, 2007.ENGLISH ABSTRACT: Invasion by the notorious tramp species, the Argentine ant (Linepithema humile Mayr) (Hymenoptera: Formicidae) has caused major concern around the globe, owing to its displacement of native ant species and other invertebrates where it invades. This species was first recorded in South Africa in 1901 in Stellenbosch, Western Cape Province (WCP), and has now become a significant pest in most urban and agricultural areas in the country. The Argentine ant has received relatively little attention in South Africa compared to other countries (e.g. California, North America). To date the extent of invasion by this species countrywide, as well as its impact on the local ant fauna inside protected areas, has not been quantified. In this study, the impact of the Argentine ant on native ant fauna inside three protected areas in the WCP (Helderberg Nature Reserve (HNR), Jonkershoek Nature Reserve (JNR) and Kogelberg Biosphere Reserve KBR)) was assessed. Species richness and diversity were compared between invaded and uninvaded bait stations at each protected area. Several native ant species were found to be displaced by the Argentine ant from all three protected areas, although three species: Meranoplus peringueyi, Monomorium sp. 8 and Tetramorium quadrispinosum, were found coexisting with it. Invaded bait stations had significantly lower ant species richness and species turnover than uninvaded bait stations. Uninvaded bait stations contained eight times more native ant species than invaded bait stations. Thus, the invasion of protected areas by the Argentine ant has severe negative consequences for the species richness and assemblage structure of native ants, leading to the biotic homogenization of these local ant communities. The distribution range of the Argentine ant inside the three protected areas (HNR, JNR, KBR), as well as microhabitat preferences that may facilitate the spread of this species inside these reserves, was also assessed. Helderberg Nature Reserve was the most invaded protected area, with the highest level of the Argentine ant occupancy, while JNR and KBR had lower occupancy levels. At all the three protected areas, this species was dominant at lower altitudinal areas, and also showed a clear preference for areas with high anthropogenic disturbances, i.e. around buildings and on lawns (picnic areas). In this study, there was no evidence that moisture availability facilitates the distribution and spread of the Argentine ant inside these reserves. Finally, a combination of published literature records, museum records and records collected in the current study was used to quantify the current distributional extent of the Argentine ant throughout urban South Africa. This is the first study quantifying the distribution and extent of invasion by the Argentine ant throughout the country. The Argentine ant was found in six of the nine South African Provinces, and its extent of occurrence includes approximately half of the country’s land surface area. Discontinuities in the distribution of the Argentine ant across the country revealed that range expansion of the Argentine ant in South Africa is occurring predominantly via human-mediated jump dispersal, rather than naturally via nest diffusion. This study clearly demonstrated that the Argentine ant is well established across South Africa as well as inside protected areas. The Argentine ant invasion was influenced by the presence of human modified landscapes (i.e. buildings) both at low and high altitude, and this was associated with higher rates of native ant species displacement at these areas. Therefore, limiting the development of recreational areas, such as buildings and picnic sites inside protected areas will result in the lower rate of spread of the Argentine ant. This will in turn lower the extent of displacement of native ant species.AFRIKAANSE OPSOMMING: Indringing deur die Argentynse mier (Linepithema humile Mayr) (Hymenoptera: Formicidae) is ‘n bron van groot kommer regoor die wêreld, as gevolg van sy vermoë om inheemse mier spesies en ander ongewerweldes te verplaas. Hierdie spesie is vir die eerste keer aangeteken in Suid-Afrika in 1901, in Stellenbosch, Weskaap Provinsie (WCP), en het ‘n belangrike pes geword in die meeste stedelike en landelike gebiede in die land. Die Argentynse mier het betreklik min aandag gekry in Suid-Afrika, in vergelyking met ander lande (bv. California, Noord Amerika). Tans is die omvang van die landwye indringing van hierdie spesie, sowel as sy impak op die plaaslike mier fauna binne beskermde areas, nog nie bepaal nie. In hierdie studie word die impak van die Argentynse mier op die inheemse mier fauna binne drie beskermde areas in die WCP (Helderberg Natuurreservaat (HNR), Jonkershoek Natuurreservaat (JNR) en Kogelberg Biosfeerreservaat (KBR)) bepaal. Spesierykheid en diversiteit was vergelyk tussen ingedringde en oningedringde lokaas stasies in elke beskermde area. Verskeie inheemse mier spesies was deur die Argentynse mier verplaas in al drie beskermde areas, alhoewel drie spesies: Meranoplus peringueyi, Monomorium sp. 8 en Tetramorium quadrispinosum het saam met dit voorgekom. Ingedringde lokaas stasies het beduidend laer mier spesierykheid en spesies omset gehad as oningedringde lokaas stasies. Dus, die indringing van beskermde areas deur die Argentynse mier het ernstige negatiewe gevolge vir die spesierykheid en gemeenskap struktuur van inheemse miere, wat lei tot die biotiese verarming van hierdie plaaslike mier gemeenskappe. Die verspreidingsarea van die Argentynse mier binne die drie beskermde areas (HNR, JNR, KBR), en die mikrohabitat voorkeure wat die verspreiding van die spesie binne hierdie reservate kan vergemaklik, was ook vasgestel. Helderberg Natuurreservaat was die mees ingedringde beskermde area, met die hoogste vlak van Argentynse mier besetting, terwyl JNR en KBR laer besettingsvlakke gehad het. By al drie die beskermde areas was hierdie spesie dominant by laer hoogtes bo seevlak en het ‘n duidelike voorkeur getoon vir areas met hoë menslike versteuring d.i. rondom geboue en op grasperke (piekniek areas). In hierdie studie was daar geen bewyse dat vog beskikbaarheid die voorkoms en verspreiding van die Argentynse mier binne die reservate vergemaklik nie. Ten slotte, ‘n kombinasie van gepubliseerde literatuur verslae, museum dokumente en verslae wat in hierdie studie versamel is, was gebruik om die huidige verspreidingsomvang van die Argentynse mier te bepaal. Dit is die eerste studie wat die verspreiding en omvang van indringing in stedelike Suid Afrika van die Argentynse mier dwarsdeur die land bepaal. Die Argentynse mier is gevind in ses van die nege provinsies in Suid-Afrika, en die omvang van sy voorkoms sluit bykans die helfte van die land se landoppervlaksarea in. Onderbrekings in die verspreiding van die Argentynse mier deur die land het blootgelê dat die uitbreiding van die voorkomsgebied van die Argentynse mier in Suid-Afrika hoofsaaklik gebeur deur mens bemiddelde verspreiding eerder as natuurlike nesverspreiding. Hierdie studie het duidelik gedemonstreer dat die Argentynse mier goed gevestig is regoor Suid-Afrika sowel as in beskermde areas. Die Argentynse mier indringing was beïnvloed deur mensgewysigde landskappe (d.i. geboue) by lae en hoë hoogtes bo seevlak, en dit was verwant aan hoër vlakke van verplasing van inheemse mier species in hierdie areas. Dus, die beperking van ontwikkeling van rekreasie areas, soos geboue en piekniekareas, in beskermde gebiede sal lei tot laer vlakke van verspreiding van die Argentynse mier. Dit sal, op sy beurt, die omvang van verplasing van die inheemse mier spesies verminder

An improved model for provision of rural community-based health rehabilitation services in Vhembe District, Limpopo Province of South Africa

Background: In 1991, Riakona Community Rehabilitation Programme initiated community-based rehabilitation (CBR) in the Vhembe District of Limpopo Province. Subsequently, the South African government adopted the programme. Aim: The aim of the study was to suggest an improvement in the model of providing CBR services. Setting: The study was conducted in six rehabilitation centres located in hospitals in the Vhembe District in Limpopo Province of South Africa. Method: A mixed-mode research design with qualitative and quantitative elements was used to conduct the study. Content analysis, the chi-square test for Goodness of Fit and the Kruskal–Wallis and Mann–Whitney non-parametric tests were conducted. Results: The key determinants of client satisfaction with the services that the community rehabilitation workers rendered included provision of assistive devices and the adoption of a holistic approach to their work. Overall, satisfaction per domain for each one of the five domains of satisfaction scored less than 90%. More than 80% of clients were satisfied with empathy (83%) and assurance (80%) domains. Tangibles, reliability and responsiveness domains had scores of 78%, 72% and 67%, respectively. These results, together with the reasoning map of conceptual framework description, were used as the building blocks of the CBR model. Conclusion: The improved CBR model is useful for putting the programme into practice. This is particularly so for the CBR managers in the districts of the Limpopo Province. Keywords: client satisfaction, disability, community-based rehabilitation, community rehabilitation worke

Penta-carbonyl-2 κ5C-chlorido-1κCl-bis- [1(η5)-cyclo-penta-dien-yl][2-oxido(meth-yl)methyl- ene-1:22 O:C]tungsten(0)zirconium(IV)

The title compound, [ZrW(C5H5)2(C2H3O)Cl(CO)5] or [W(CO)5C(CH3)OZr(C5H5) 2Cl], consists of two metal centres, with a (tungsten penta-carbon-yl)oxymethyl- carbene group coordinating as a monodentate ligand to the chloridozirconocene. The two halves of the mol-ecule are related by a crystallographic mirror plane. Delocalization through the Zr - O - C=W unit is indicated by a short Zr - O distance and a nearly linear Zr - O - C angle.Articl